Past population dynamics in Africa have remained largely elusive due to the lack of demographic data. Researchers are understandably deterred from trying to explain what is not known and African historical population estimates suffer from this lack of interest. In this paper I explain present day African population densities using mostly ecological factors as explanatory variables. I find evidence supporting the view that ecological factors deeply affected precolonial patterns of human settlement in Sub-Saharan Africa. Human populations grew relatively large in the presence of lakes, highlands, or when situated in the wet, coastal regions of Western Africa. Other environmental suites were thinly populated with overall population sizes stagnant at low or very low steady states. Subsequent developments show that dramatic increases in the agricultural productivity of peripheral, semiarid areas were possible once colonial innovations were on hand. Thus, European colonization had likely asymmetric effects on the population dynamics of different regions of Africa.